The 3rd annual Many Hosts of Mycobacteria meeting will be held at a historic former leprosy sanatorium in Carville, Louisiana in November 2009. This meeting is co-organized by Michelle Larsen (Albert Einstein College of Medicine) and Ray Waters (National Animal Disease Center, USDA) in consultation with Christine Sizemore (NIAID). The purpose of the meeting series is to bring together basic researchers, clinicians, and veterinary medicine researchers that study mycobacterial diseases/hosts. The first meeting in September 2007 was held at the National Animal Disease Center in Ames, Iowa and the second meeting was held in September 2008 in Gettysburg, Pennsylvania. These meetings are small (~70-80 attendees) and have open registration. A workshop format is used for the meetings to foster open and interactive discussion. The diverse perspectives are exemplified by inclusion of thirteen models (mouse, guinea pig, cotton rat, rabbit, badger, possum, armadillo, fish, deer, cattle, elephant, monkeys and humans) and both experimental and natural infections (Tuberculosis from M. bovis and M. tuberculosis;Leprosy from M. leprae, Johnes Disease from M. avium paratuberculosis, and general mycobacterial infections from M. ulcerans and non-tuberculous mycobacteria). The focus of the Iowa meeting was on the utility and limitations of these models in understanding myobacterial disease, pathogenesis, and vaccine development. The Gettysburg meeting focused on immunopathology, and the theme of the Carville meeting will be on comparative mycobacteriology. We target inclusion of young investigators as speakers and moderators for these meetings to foster discussion of new ideas and allow for development of collaboration between research groups that do not typically interact with each other.